Electrolytic recovery of zinc and manganese.



ITED STATES PATENT OFFICE.

ANDREW GORDON FRENCH, OI NELSON, BRITISH COLUMBIA, CANADA.

ELECTROLYTIC RECOVERY OF ZINC AND KANGANEQE.

No Drawing.

Specification of Letters Patent.

Application filed September 4, 1912. Serial No. 718,506.

Patented Mar. 4, 1913.

To all whom it may concern:

Be it known that. I, ANDREW GORDON FRENCH, a citizen of the Dominion ofCanada, residing at Nelson, in the Province of British Columbia, Canada,have invented a new and useful Electrolytic Recovery of Zinc andManganese, of which the following is a specification.-

This invention relates to a process for the recove of metallic zinc andmanganese dioxid y electrolysis, the object being to recover thesematerials in a dense, pure form in the case of zinc, and in a puremarketable condition in the case of the manganese dioxid. It forms partof a treatment for the recovery of these materials from refrac- "torycomplex zinc-lead ores containing manganese. The preparatory treatmentof these ores is set forth in an application for a patent, now pending,whic was filed on the 30th of September, 1911, under Serial No. 652,047,patented October 15, 1912, #1,o41,0e0.

In the process set forth in that application the final result was astrong, aqueous solution of sulfate of zinc with neutral sulfate ofsodium and containing more or less sulfate of manganese, which isusually present in the complex ores which this process is designed totreat. These three salts, when in solution to ether, are easily split upby a low voltage direct electric current and yields on the cathode adense deposit of very pure, metallic zinc and on the anode puremanganese dioxid. 'It is on the favorable combination of these threesalts that the success of this process depends and where the manganeseis not in sufiicient quantity to form that favorable combination, thiselement should be added-in order to obtain the mostsatisfactory results.

The following specification fully describes the process as. conducted.

' as a dense deposit on the cathodes and a pure manganese dioxid at theanodes.

The purity of the zinc, particularly in its absolute freedom from oxidof zinc and sulfur compounds, the presence of which in previous attemptsat electrolytic recovery have caused sponginess and deterioration of 50the deposit, is attributable chiefly to the ass'oclation with the zincin the electrolyte, of the manganese and sodium sulfates. These threesalts in solution to ether, when crystallized out do so as a trip esalt. A further advantageous feature of this treatment lies in the factthat the sulfuric acid which is liberated from the zinc and man anesesulfates combines in its nascent con ition with the neutral sulfate ofsodium to form bisulfate and persulfate of sodium in the electrolyte,and as these reactions are exothermic' the current is correspondinglyreinforced. A second reinforcement in a similar manner is obtained fromthe formation of the manganese dioxid at the anode.

In the practice of the process, the solution, which forms theelectrolyte, is made to flow continuously from the ore leaching tanksinto the electrolytic tank, in a nearly saturated condition and freefrom acidity, and a return flow of the electrolyte, after having beenpartially acted upon by the current, is returned from the electrolytictank to the ore leaching tank. A proportion of the zinc and themanganese having been abstracted from the solution and depositedrespectively on the cathodes and at the anodes, the return flow of thesolution to the leaching tank is in an acid condition, having from oneand a half to two and a half per cent. of acidity as bisulfate andpersulfate of sodium. This acidity enables it to dissolve out a freshsupply of zinc and manganese in the leaching tank, and this process iscontinued until the ore. in the leaching tank is depleted of its zincand manganese.

As described above, when treating solutions from ores which'are poor inmanganese, it is necessary to mix it with others richer in that. elementso as to give one unit of manganese to from four to six units of zinc,which I find to be a good working proportion although if a greaterproportion of manganese be employed the operation may still besuccessfully performed.

In circumstances where ores sufiiciently rich in manganese are notobtainable, I obtain the required sulfate of manganese by treating aproportion of the manganese dioxid mud, as deposited at the anodes, withsulfurous acid gas, either free or in solution, while the dioxid iscarried in 'as small a quantit of water as will hold it in suspen-S1011. 'l his immediately takes oxygen from the dioxid forming thesoluble manganese sulfate which is required to add to the electrolyte.

The sulfurous acid may be obtained from the flues of the furnace usedfor calciningthe sulfid ores in the earlier treatment re ferred to, asbeing the subject of the application filed September 30, 1911 andhereinbefore referred to. I

The process here described is advantageous in that it produces aparticularly dense and pure form of. metallic zinc, and

similarly the dioxid of manganese is comof the required sulfate ofmanganese by treating-dioxid of manganese in suspension in water bysulfurous acid gas or a sulfurousacid solution, is employed, since thatform of the invention constitutes the subject-matter of my divisionalapplication filed on February 4, 1913, Serial No. 746121.

Having now particularly described my invention I hereby declare thatwhat I claim as new and desire-to be protected in by Letters Patent, is:

3. A process for the recovery of pure I metallic zinc and manganese'dioxid, said process comprising the passage of an elec-' tric currentof from two and a half to four and a half volts from. a lead anodeto azinc cathode immersed in a solution containing sulfate of zinc, sulfateof manganese-and neutral sulfate of sodium.

4. A process for the recovery of pure metallic zinc and manganesedioxid, said process comprising the electrolytic decomposition of asolution containing sulfate of zinc, sulfate of, manganese and neutralsulfate of sodium the electrolyte after being acted uponbeingcontinuousl delivered to the leaching tank from which the originalsupply was obtained and continually replaced in the electrolytic tank bya supply drawn from the same leaching tank.

In testimony whereof I have signed my name to thisspecification in thepresence of two subscribing witnesses.

ANDREW GORDON FRENCH.

Witnesses:

WM. .0. MCCLELLAND, W. F. TEETZEL.

